Hi
Are you able to successfully log in to your myAT&T account online? If your myAT&T account includes an extra layer of security (prompts you to enter your security passcode AFTER you’ve entered your login credentials,) that feature may need to be disabled in order for Mint to sync. You can do this under myAT&T > Profile > Security Passcode > Extra security (turn off.)
Does your AT&T account include wireless only? Or is your bill unified with U-verse or DIRECTV? If unified/combined, there is a chance that Mint will require the bills to be separated before it can properly distinguish them.
Thanks,
Kevin
